Multi-band power amplifier

ABSTRACT

An apparatus includes a first capacitor, an inductor coupled to the first capacitor, and a second capacitor coupled to the inductor. The second capacitor is coupled to a first output of a differential amplifier.

I. FIELD

The present disclosure is generally related to a multi-band poweramplifier.

II. DESCRIPTION OF RELATED ART

Advances in technology have resulted in smaller and more powerfulcomputing devices. For example, there currently exist a variety ofportable personal computing devices, including wireless computingdevices, such as portable wireless telephones, personal digitalassistants (PDAs), and paging devices that are small, lightweight, andeasily carried by users. More specifically, portable wirelesstelephones, such as cellular telephones and Internet protocol (IP)telephones, can communicate voice and data packets over wirelessnetworks. Further, many such wireless telephones include other types ofdevices that are incorporated therein. For example, a wireless telephonecan also include a digital still camera, a digital video camera, adigital recorder, and an audio file player. Also, such wirelesstelephones can process executable instructions, including softwareapplications, such as a web browser application, that can be used toaccess the Internet. As such, these wireless telephones can includesignificant computing capabilities.

Wireless devices may include multiple power amplifiers and driveramplifiers to transmit signals over multiple frequency bands. Forexample, a first driver amplifier and a first power amplifier may beconfigurable to transmit signals over a first frequency band (e.g., a2.4 Gigahertz (GHz) band). Additionally, a second driver amplifier and asecond power amplifier may be configurable to transmit signals over asecond frequency band (e.g., a 5.6 GHz band). Using multiple driveramplifiers and multiple power amplifiers for multi-band transmissions(e.g., dual-band transmissions) may increase die area. For example, atransistor core for each driver amplifier and a transistor core for eachpower amplifier may be relatively large (e.g., in the millimeter (mm)range), which may increase the chip size, die area, and cost of thedriver amplifiers and power amplifiers.

III. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless device communicating with a wireless system;

FIG. 2 shows a block diagram of the wireless device in FIG. 1;

FIG. 3 is a diagram that depicts an exemplary embodiment of a dual-bandpower amplifier having a differential amplifier including a singletransistor core;

FIG. 4 is a diagram that depicts an exemplary embodiment of a tri-bandpower amplifier having a differential amplifier including a singletransistor core;

FIG. 5 is a diagram the depicts an exemplary embodiment of a multi-banddriver amplifier having a differential amplifier including a singletransistor core;

FIG. 6 is a diagram the depicts another exemplary embodiment of amulti-band driver amplifier having a differential amplifier including asingle transistor core; and

FIG. 7 is a flowchart that illustrates an exemplary embodiment of amethod of operating a multi-band power amplifier.

IV. DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofexemplary designs of the present disclosure and is not intended torepresent the only designs in which the present disclosure can bepracticed. The term “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other designs. The detailed description includesspecific details for the purpose of providing a thorough understandingof the exemplary designs of the present disclosure. It will be apparentto those skilled in the art that the exemplary designs described hereinmay be practiced without these specific details. In some instances,well-known structures and devices are shown in block diagram form inorder to avoid obscuring the novelty of the exemplary designs presentedherein.

FIG. 1 shows a wireless device 110 communicating with a wirelesscommunication system 120. Wireless communication system 120 may be aLong Term Evolution (LTE) system, a Code Division Multiple Access (CDMA)system, a Global System for Mobile Communications (GSM) system, awireless local area network (WLAN) system, or some other wirelesssystem. A CDMA system may implement Wideband CDMA (WCDMA), CDMA 1X,Evolution-Data Optimized (EVDO), Time Division Synchronous CDMA(TD-SCDMA), or some other version of CDMA. For simplicity, FIG. 1 showswireless communication system 120 including two base stations 130 and132 and one system controller 140. In general, a wireless system mayinclude any number of base stations and any set of network entities.

Wireless device 110 may also be referred to as a user equipment (UE), amobile station, a terminal, an access terminal, a subscriber unit, astation, etc. Wireless device 110 may be a cellular phone, a smartphone,a tablet, a wireless modem, a personal digital assistant (PDA), ahandheld device, a laptop computer, a smartbook, a netbook, a cordlessphone, a wireless local loop (WLL) station, a Bluetooth device, etc.Wireless device 110 may communicate with wireless system 120. Wirelessdevice 110 may also receive signals from broadcast stations (e.g., abroadcast station 134), signals from satellites (e.g., a satellite 150)in one or more global navigation satellite systems (GNSS), etc. Wirelessdevice 110 may support one or more radio technologies for wirelesscommunication such as LTE, WCDMA, CDMA 1X, EVDO, TD-SCDMA, GSM, 802.11,etc.

FIG. 2 shows a block diagram of an exemplary design of wireless device110 in FIG. 1. In this exemplary design, wireless device 110 includes atransceiver 220 coupled to a primary antenna 210, a transceiver 222coupled to a secondary antenna 212, and a data processor/controller 280.Transceiver 220 includes multiple (K) receiver paths 230 pa to 230 pkand multiple (K) transmitter paths 250 pa to 250 pk to support multiplefrequency bands, multiple radio technologies, carrier aggregation, etc.Transceiver 222 includes multiple (L) receiver paths 230 sa to 230 sland multiple (L) transmitter paths 250 sa to 250 sl to support multiplefrequency bands, multiple radio technologies, carrier aggregation,receive diversity, multiple-input multiple-output (MIMO) transmissionfrom multiple transmit antennas to multiple receive antennas, etc.

In the exemplary design shown in FIG. 2, each receiver path 230 pa, 230pk, 230 sa, 230 sl includes an LNA 240 pa, 240 pk, 240 sa, 240 sl and areceive circuit 242 pa, 242 pk, 242 sa, 242 sl, respectively. For datareception, antenna 210 receives signals from base stations and/or othertransmitter stations and provides a received RF signal, which is routedthrough an antenna interface circuit 224 and presented as an input RFsignal to a selected receiver. Antenna interface circuit 224 may includeswitches, duplexers, transmit filters, receive filters, matchingcircuits, etc. The description below assumes that receiver path 230 pais the selected receiver path. Within the receiver path 230 pa, an LNA240 pa amplifies the input RF signal and provides an output RF signal.Receive circuits 242 pa downconvert the output RF signal from RF tobaseband, amplify and filter the downconverted signal, and provide ananalog input signal to data processor 280. Receive circuits 242 pa mayinclude mixers, filters, amplifiers, matching circuits, an oscillator, alocal oscillator (LO) generator, a phase locked loop (PLL), etc. Eachremaining receiver paths 230 pk, 230 sa, 230 sl in transceivers 220 and222 may operate in a similar manner as receiver path 230 pa.

In the exemplary design shown in FIG. 2, each transmitter path 250 pa,250 pk, 250 sa, 250 sl includes a transmit circuit 252 pa, 252 pk, 252sa, 252 sl and a power amplifier (PA) 254 pa, 254 pk, 254 sa, 254 sl,respectively. For data transmission, data processor 280 processes (e.g.,encodes and modulates) data to be transmitted and provides an analogoutput signal to a selected transmitter. The description below assumesthat transmitter path 250 pa is the selected transmitter path. Withintransmitter path 250 pa, transmit circuits 252 pa amplify, filter, andupconvert the analog output signal from baseband to RF and provide amodulated RF signal. Transmit circuits 252 pa may include amplifiers,filters, mixers, matching circuits, an oscillator, an LO generator, aPLL, etc. A PA 254 pa receives and amplifies the modulated RF signal andprovides a transmit RF signal having the proper output power level. Thetransmit RF signal is routed through antenna interface circuit 224 andtransmitted via antenna 210. Each remaining transmitter path 250 pk, 250sa, 250 sl in transceivers 220 and 222 may operate in similar manner astransmitter 250 pa.

FIG. 2 shows an exemplary design of receiver 230 and transmitter 250. Areceiver and a transmitter may also include other circuits not shown inFIG. 2, such as filters, matching circuits, etc. All or a portion oftransceivers 220 and 222 may be implemented on one or more analogintegrated circuits (ICs), RF ICs (RFICs), mixed-signal ICs, etc. Forexample, LNAs 240 and receive circuits 242 may be implemented on onemodule, which may be an RFIC, etc. The circuits in transceivers 220 and222 may also be implemented in other manners.

In an exemplary embodiment, the transmit circuits 252 pa, 252 pk, 252sa, 252 sl may include driver amplifiers 290 pa, 290 pk, 290 sa, 290 sl,respectively. The driver amplifiers 290 pa, 290 pk, 290 sa, 290 sl mayreceive transmission signals (e.g., input signals) from the controller280. One or more of the driver amplifiers 290 pa, 290 pk, 290 sa, 290 slmay be a multi-band driver amplifier having a single transistor core,such as the multi-band driver amplifier 500 as described in furtherdetail with respect to FIG. 5 or the multi-band driver amplifier 600 asdescribed in further detail with respect to FIG. 6. For example, one ormore of the driver amplifiers 290 pa, 290 pk, 290 sa, 290 sl may receivea control signal from control circuitry 284 to selectively operate in afirst frequency band, a second frequency band, or any combinationthereof. The driver amplifiers 290 pa, 290 pk, 290 sa, 290 sl mayprovide amplified transmission signals 294 pa, 294 pk, 294 sa, 294 sl tothe power amplifiers 254 pa, 254 pk, 254 sa, 254 sl, respectively.

In an exemplary embodiment, the power amplifiers 254 pa, 254 pk, 254 sa,254 sl may receive output signals from the driver amplifiers 290 pa, 290pk, 290 sa, 290 sl, respectively. One or more of the power amplifiers254 pa, 254 pk, 254 sa, 254 sl may be a multi-band power amplifier. Forexample, one or more of the power amplifiers 254 pa, 254 pk, 254 sa, 254sl may include dual-band power amplification circuitry having a singledifferential amplifier (e.g., a single transistor core), such as thedual-band power amplification circuitry 300 as described in furtherdetail with respect to FIG. 3. In addition, or in the alternative, oneor more of the power amplifiers 254 pa, 254 pk, 254 sa, 254 sl mayinclude tri-band amplification circuitry having a differential amplifier(e.g., a single transistor core), such as the tri-band power amplifier400 as described in further detail with respect to FIG. 4. In anexemplary embodiment, one or more of the power amplifiers 254 pa, 254pk, 254 sa, 254 sl may receive a control signal (e.g., a control signal299 pa) from the control circuitry 284 to selectively operate in a firstfrequency band, a second frequency band, a third frequency band, or anycombination thereof. As described in greater detail with respect to FIG.3, the control signal 299 pa may include a first enable signal(First_EN), a second enable signal (Second_EN), and/or a transmissionenable signal (TX_EN). The amplification circuitry 300 may provide anamplified signal 296 pa (e.g., an output signal of the power amplifier254 pa) to the antenna interface circuit 224.

Data processor/controller 280 may perform various functions for wirelessdevice 110. For example, data processor 280 may perform processing fordata being received via receivers 230 and data being transmitted viatransmitters 250. Controller 280 may control the operation of thevarious circuits within transceivers 220 and 222. For example, thecontroller 280 may include control circuitry 284 to bias one or more ofthe power amplifiers 254 pa, 254 pk, 254 sa, 254 sl and/or one or moreof the driver amplifiers 290 pa, 290 pk, 290 sa, 290 sl to operate in afirst frequency band, a second frequency band, or any combinationthereof. A memory 282 may store program code and data for dataprocessor/controller 280. Data processor/controller 280 may beimplemented on one or more application specific integrated circuits(ASICs) and/or other ICs.

Wireless device 110 may support multiple band groups, multiple radiotechnologies, and/or multiple antennas. Wireless device 110 may includea number of LNAs to support reception via the multiple band groups,multiple radio technologies, and/or multiple antennas.

Referring to FIG. 3, a diagram of a dual-band power amplifier 300 havinga differential amplifier 302 including a single transistor core isshown. In an exemplary embodiment, the power amplifier 300 maycorrespond to, or be included in, one or more of the power amplifiers254 pa-254 pk, 254 sa-254 sl of FIG. 2. The power amplifier 300 mayreceive control signals (e.g., a transmission enable signal (TX_EN), afirst enable signal (First_EN), and a second enable signal (Second_EN))from control circuitry (e.g., the control circuitry 284) to selectivelyoperate in a first frequency band, in a second frequency band, or toconcurrently operate in the first and second frequency bands. Thecontrols signals may correspond to the control signal 299 pa of FIG. 2.In an exemplary embodiment, the power amplifier 300 may be tunable inbroadband frequency ranges. For example, the power amplifier 300 may betuned to operate within a broad frequency spectrum (e.g., an extensivefrequency range) having a communication bandwidth of at least 256kilobits per second.

The power amplifier 300 may include a differential amplifier 302 (e.g.,a transistor core) and a transformer 304 (e.g., an output balun). Thedifferential amplifier 302 may include a transistor 306, a transistor308, a transistor 310, and a transistor 312. In an exemplary embodiment,the transistors 306-312 of the differential amplifier 302 may be n-typemetal oxide semiconductor (NMOS) transistors. The transistor 306 and thetransistor 308 form a differential transistor pair. A source of thetransistor 306 and a source of the transistor 308 may be coupled toground. A gate of the transistor 306 and a gate of the transistor 308may be coupled to receive a differential input signal (IN+, IN−). Toillustrate, the gate of the transistor 306 and the gate of thetransistor 308 may be coupled to receive the amplified transmissionsignals 294 pa of FIG. 2 from the driver amplifier 290 pa. A drain ofthe transistor 306 may be coupled to a source of the transistor 310, anda drain of the transistor 308 may be coupled to a source of thetransistor 312.

The differential amplifier 302 may be coupled to the transformer 304.The transformer 304 may include an inductor 322 that iselectromagnetically coupled to an inductor 324. A drain of thetransistor 310 may be coupled to a first terminal of the inductor 322,and a drain of the transistor 312 may be coupled to a second terminal ofthe inductor 322. The transformer 304 may transfer energy from theinductor 322 (e.g., a primary winding) to the inductor 324 (e.g., asecondary winding) to generate an output of the power amplifier 300 atthe inductor 324. For example, the output of the power amplifier 300 maycorrespond to the output signal 296 pa that propagates through theinductor 324 based on the magnetic field and mutual induction betweenthe primary and secondary windings. In an exemplary embodiment, theoutput of the power amplifier 300 may be provided to an antennainterface circuit (e.g., the antenna interface circuit 224 of FIG. 2 orthe antenna interface circuit 226 of FIG. 2).

A first terminal of a capacitor 314 may be coupled to the drain of thetransistor 310, and a second terminal of the capacitor 314 may becoupled to a drain of a transistor 318. In a similar manner, a firstterminal of a capacitor 316 may be coupled to the drain of thetransistor 312, and a second terminal of the capacitor 316 may becoupled to a drain of a transistor 320. In an exemplary embodiment, thetransistors 318, 320 are NMOS transistors. A source of the transistor318 and a source of the transistor 320 may be coupled to ground. A gateof the transistor 318 and a gate of the transistor 320 may be coupled toreceive the transmission enable signal (TX_EN).

A first terminal of a capacitor 326 may be coupled to the drain of thetransistor 310, and a second terminal of the capacitor 326 may becoupled to a first terminal of an inductor 330. A first terminal of acapacitor 328 may be coupled to the drain of the transistor 312, and asecond terminal of the capacitor 328 may be coupled to a second terminalof the inductor 330. The first terminal of the inductor 330 may becoupled to a drain of a transistor 332, and the second terminal of theinductor 330 may be coupled to a drain of a transistor 334. In anexemplary embodiment, the transistors 332, 334 are NMOS transistors. Asource of the transistor 332 and a source of the transistor 334 arecoupled to ground. A gate of the transistor 332 and a gate of thetransistor 334 may be coupled to receive the first enable signal(First_EN).

A first terminal of a capacitor 336 may be coupled to the first terminalof the inductor 330, and a first terminal of a capacitor 338 may becoupled to the second terminal of the inductor 330. A second terminal ofthe capacitor 336 may be coupled to a drain of a transistor 340, and asecond terminal of the capacitor 338 may be coupled to a drain of atransistor 342. In an exemplary embodiment, each capacitor 336, 338represents a tunable capacitor bank. For example, each capacitor 336,338 may represent multiple capacitor branches coupled in parallel. Eachcapacitor branch may include a switch (e.g., a transistor) coupled inseries with a capacitor. To increase the capacitance of the tunablecapacitor banks 336, 338, a control signal (from the control circuitry284 of FIG. 2) may activate a switch to “turn on” a correspondingcapacitor branch. In another exemplary embodiment, the capacitors 336,338 may be single capacitors.

In an exemplary embodiment, the transistors 340, 342 are NMOStransistors. A source of the transistor 340 and a source of thetransistor 342 are coupled to ground. A gate of the transistor 340 and agate of the transistor 342 may be coupled to receive the second enablesignal (Second_EN).

During operation, a first differential input signal (IN+) may beprovided to the transistor 306 such that the first differential inputsignal (IN+) propagates along a first path when the transistor 310 isenabled, and a second differential input signal (IN−) may be provided tothe transistor 308 such that the second differential input signal (IN−)propagates along a second path when the transistor 312 is enabled. Thefirst path includes the capacitor 314, the inductor 322, the capacitor326, the inductor 330, and the capacitor 336. The second path includesthe capacitor 316, the inductor 322, the capacitor 328, the inductor330, and the capacitor 338.

To operate in a first frequency band (e.g., a 2.4 GHz frequency band),the transmission enable signal (TX_EN) may activate the transistor 318(e.g., a shunt-to ground transistor) and the first enable signal(First_EN) may activate the transistor 334 (e.g., a shunt-to-groundtransistor). For example, the transmission enable signal (TX_EN) may beat a logical high voltage level and enable conduction of the transistor318. Additionally, the first enable signal (First_EN) may be at alogical high voltage level and enable conduction of the transistor 334.Thus, the capacitor 314 may be shunt to ground and additional currentmay charge the capacitor 326 and additional current may propagatethrough the inductor 330 (e.g., the inductor 330 may be coupled toground via the transistor 334). Current based on the first differentialinput signal (IN+) may charge the capacitor 314, charge the capacitor326, flow through the inductor 322, and flow through the inductor 330such that the output of the differential amplifier 302 is subject to arelatively high capacitance (e.g., the capacitance of the capacitor 314and the capacitance of the capacitor 326). Subjecting the output to thedifferential amplifier 302 to the relatively high capacitance may causethe power amplifier 300 to operate within the first frequency band.

In a similar manner, the transmission enable signal (TX_EN) may activatethe transistor 320 (e.g., a shunt-to-ground transistor) and the firstenable signal (First_EN) may activate the transistor 332 (e.g., ashunt-to-ground transistor). Thus, the capacitor 316 may be shunt toground and additional current may charge the capacitor 328 andadditional current may propagate through the inductor 330 (e.g., theinductor may be coupled to ground via the transistor 332). Current basedon the second differential input signal (IN−) may charge the capacitor316, charge the capacitor 328, flow through the inductor 322, and flowthrough the inductor 330 such that the output of the differentialamplifier 302 is subject to a relatively high capacitance (e.g., thecapacitance of the capacitor 316 and the capacitance of the capacitor328). Subjecting the output of the differential amplifier 302 to therelatively high capacitance may cause the power amplifier 300 to operatewithin the first frequency band.

To operate in a second frequency band (e.g., a 5.6 GHz frequency band),the transmission enable signal (TX_EN) may activate the transistor 318and the capacitor 314 may be shunt to ground. In addition, the firstenable signal (First_EN) may disable the transistor 334 to decouple theinductor 330 from ground such that the capacitor 326 is a “floating”capacitor. For example, the first enable signal (First_EN) may have alogical low voltage level and may disable (e.g., turn off) conduction ofthe transistor 334. Thus, current based on the first differential inputsignal (IN+) may charge the capacitor 314 and flow through the inductor322 such that the output of the differential amplifier 302 is subject toa reduced capacitance (e.g., a capacitance based on the capacitor 314 asopposed to a capacitance based on the capacitor 314 and the capacitor326). Subjecting the output of the differential amplifier 302 to thereduced capacitance may cause the power amplifier 300 to operate withinthe second frequency band.

In a similar manner, the transmission enable signal (TX_EN) may activatethe transistor 320 and the capacitor 316 may be shunt to ground. Inaddition, the first enable signal (First_EN) may disable the transistor332 to decouple the inductor 330 from ground such that the capacitor 328is a “floating” capacitor. Current based on the second differentialinput signal (IN−) may charge the capacitor 316 and flow through theinductor 322 such that the output of the differential amplifier 302 issubject to a reduced capacitance (e.g., a capacitance based on thecapacitor 316 as opposed to a capacitance based on the capacitor 316 andthe capacitor 328). Subjecting the output of the differential amplifier302 to the reduced capacitance may cause the power amplifier 300 tooperate within the second frequency band.

In an exemplary embodiment, the power amplifier 300 may concurrentlyoperate in the first frequency band and the second frequency band. Forexample, the second enable signal (Second_EN) may enable the transistors340, 342 such that the output of the differential amplifier 302 isadditionally subject to the capacitance of the capacitors 336, 338. Theincreased capacitance may cause the cause the power amplifier 300 tooperate within the first frequency band (e.g., the 2.4 GHz frequencyband) in addition to operating within the second frequency band. Forexample, the increased capacitance may cause the inductive andcapacitive elements coupled to the output of the differential amplifier302 to resonate at approximately 2.4 GHz and at approximately 5.6 GHz.

The power amplifier 300 of FIG. 3 may reduce die area and increase costsavings by utilizing a single differential amplifier 302 (as opposed tomultiple transistor cores) to operate within one or more frequency bands(e.g., transmit over one or more frequency bands). Onecapacitor-inductor-capacitor (CLC) network may be coupled to the primarycoil (e.g., the inductor 322) of the transformer 304 (e.g., the outputbalun). For example, the CLC network (e.g., the capacitor 326, theinductor 330, and the capacitor 328) may be coupled to the inductor 322and configured to operate within the first frequency band. In addition,the CLC network may be decoupled from the inductor 322 to configure thepower amplifier 300 to operate within the second frequency band. It willalso be appreciated that operating the power amplifier 300 within thefirst frequency band (e.g., 2.4 GHz) and/or the second frequency band(e.g., 5.6 GHz) may facilitate communication based on a wirelesscommunications standard, such as an Institute of Electrical andElectronics Engineers (IEEE) 802.11 standard. For example, the poweramplifier 300 may facilitate communication based on an IEEE 802.11aprotocol, an IEEE 802.11b protocol, an 802.11g protocol, an IEEE 802.11nprotocol, and/or an IEEE 802.11 ac protocol.

Referring to FIG. 4, a diagram of a tri-band power amplifier 400 havinga differential amplifier 402 including a single transistor core isshown. In an exemplary embodiment, the power amplifier 400 maycorrespond to, or may be included in, one or more of the poweramplifiers 254 pa-254 pk, 254 sa-254 sl of FIG. 2. The power amplifier400 may receive control signals (e.g., a transmission enable signal(TX_EN), a first enable signal (First_EN), a second enable signal(Second_EN), and a third enable signal (Third_EN)) from controlcircuitry (e.g., the control circuitry 284) to selectively operate in afirst frequency band, in a second frequency band, or in a thirdfrequency band. In an exemplary embodiment, the power amplifier 400 maybe tunable in broadband frequency ranges. For example, the poweramplifier 400 may be tuned to operate within a broad frequency spectrum(e.g., an extensive frequency range) having a communication bandwidth ofat least 256 kilobits per second.

The power amplifier 400 may include a differential amplifier 402 (e.g.,a transistor core) and a transformer 404 (e.g., an output balun). Thedifferential amplifier 402 may include a transistor 406, a transistor408, a transistor 410, and a transistor 412. In an exemplary embodiment,the transistors 406-412 of the differential amplifier 402 may be NMOStransistors. The transistor 406 and the transistor 408 form adifferential transistor pair. A source of the transistor 406 and asource of the transistor 408 may be coupled to ground. A gate of thetransistor 406 and a gate of the transistor 408 may be coupled toreceive a differential input signal (IN+, IN−). To illustrate, the gateof the transistor 406 and the gate of the transistor 408 may be coupledto receive one of the amplified transmission signals 294 pa, 294 pk, 294sa, 294 sl of FIG. 2 from a corresponding driver amplifier 290 pa, 290pk, 290 sa, 290 sl. A drain of the transistor 406 may be coupled to asource of the transistor 410, and a drain of the transistor 408 may becoupled to a source of the transistor 412.

The differential amplifier 402 may be coupled to the transformer 404.The transformer 404 may include an inductor 422 that iselectromagnetically coupled to an inductor 424. A drain of thetransistor 410 may be coupled to a first terminal of the inductor 422,and a drain of the transistor 412 may be coupled to a second terminal ofthe inductor 422. The transformer 404 may transfer energy from theinductor 422 (e.g., a primary winding) to the inductor 424 (e.g., asecondary winding) to generate an output of the power amplifier 400 atthe inductor 424. For example, the output of the power amplifier 400 maybe the output signal 296 pa that propagates through the inductor 424based on the magnetic field and mutual induction between the primary andsecondary windings. In an exemplary embodiment, the output of the poweramplifier 400 may be provided to an antenna interface circuit (e.g., theantenna interface circuit 224 of FIG. 2 or the antenna interface circuit226 of FIG. 2).

A first terminal of a capacitor 414 may be coupled to the drain of thetransistor 410, and a second terminal of the capacitor 414 may becoupled to a drain of a transistor 418. In a similar manner, a firstterminal of a capacitor 416 may be coupled to the drain of thetransistor 412, and a second terminal of the capacitor 416 may becoupled to a drain of a transistor 420. In an exemplary embodiment, thetransistors 418, 420 are NMOS transistors. A source of the transistor418 and a source of the transistor 420 may be coupled to ground. A gateof the transistor 418 and a gate of the transistor 420 may be coupled toreceive the transmission enable signal (TX_EN).

A first terminal of a capacitor 426 may be coupled to the drain of thetransistor 410, and a second terminal of the capacitor 426 may becoupled to a first terminal of an inductor 430. A first terminal of acapacitor 428 may be coupled to the drain of the transistor 412, and asecond terminal of the capacitor 428 may be coupled to a second terminalof the inductor 430. The first terminal of the inductor 430 may becoupled to a drain of a transistor 432, and the second terminal of theinductor 430 may be coupled to a drain of a transistor 434. In anexemplary embodiment, the transistors 432, 434 are NMOS transistors. Asource of the transistor 432 and a source of the transistor 434 arecoupled to ground. A gate of the transistor 432 and a gate of thetransistor 434 may be coupled to receive the first enable signal(First_EN).

A first terminal of a capacitor 436 may be coupled to the first terminalof the inductor 430, and a first terminal of a capacitor 438 may becoupled to the second terminal of the inductor 430. A second terminal ofthe capacitor 436 may be coupled to a drain of a transistor 440, and asecond terminal of the capacitor 438 may be coupled to a drain of atransistor 442. In an exemplary embodiment, each capacitor 436, 438 mayrepresent a tunable capacitor bank. For example, each capacitor 436, 438may include multiple capacitor branches coupled in parallel. Eachcapacitor branch may include a switch (e.g., a transistor) coupled inseries with a capacitor. To increase the capacitance of the capacitors436, 438, a control signal (from the control circuitry 284 of FIG. 2)may activate a switch to “turn on” a corresponding capacitor branch. Inanother exemplary embodiment, the capacitors 436, 438 may be singlecapacitors.

In an exemplary embodiment, the transistors 440, 442 are NMOStransistors. A source of the transistor 440 and a source of thetransistor 442 are coupled to ground. A gate of the transistor 440 and agate of the transistor 442 may be coupled to receive the second enablesignal (Second_EN).

A first terminal of a capacitor 444 may be coupled to the drain of thetransistor 410, and a second terminal of the capacitor 444 may becoupled to a first terminal of an inductor 448. A first terminal of acapacitor 446 may be coupled to the drain of the transistor 412, and asecond terminal of the capacitor 446 may be coupled to a second terminalof the inductor 448. The first terminal of the inductor 448 may becoupled to a drain of a transistor 450, and the second terminal of theinductor 448 may be coupled to a drain of a transistor 452. In anexemplary embodiment, the transistors 450, 452 are NMOS transistors. Asource of the transistor 450 and a source of the transistor 452 arecoupled to ground. A gate of the transistor 450 and a gate of thetransistor 452 may be coupled to receive the third enable signal(Third_EN).

During operation, a first differential input signal (IN+) may beprovided to the transistor 406 such that the first differential inputsignal (IN+) propagates along a first path when the transistor 410 isenabled, and a second differential input signal (IN−) may be provided tothe transistor 408 such that the second differential input signal (IN−)propagates along a second path when the transistor 412 is enabled. Thefirst path includes the capacitor 414, the inductor 422, the capacitor426, the inductor 430, the capacitor 436, the capacitor 444, and theinductor 448. The second path includes the capacitor 416, the inductor422, the capacitor 428, the inductor 430, the capacitor 438, thecapacitor 446, and the inductor 448.

To operate in a first frequency band (e.g., a 2.4 GHz frequency band),the transmission enable signal (TX_EN) may activate the transistor 418(e.g., a shunt-to ground transistor), the first enable signal (First_EN)may activate the transistor 434 (e.g., a shunt-to-ground transistor),and the third enable signal (Third_EN) may deactivate the transistor 452(e.g., a shunt-to-ground transistor). For example, the transmissionenable signal (TX_EN) may be at a logical high voltage level and enableconduction of the transistor 418, the first enable signal (First_EN) maybe at a logical high voltage level and enable conduction of thetransistor 434, and the third enable signal (Third_EN) may be a logicallow voltage level to disable conduction of the transistor 452. Thus, thecapacitor 414 may be shunt to ground, additional current may charge thecapacitor 426 and additional current may propagate through the inductor430 (e.g., the inductor 430 may be coupled to ground via the transistor434), and the capacitor 444 may be decoupled from ground to operate as a“floating” capacitor. Current based on the first differential inputsignal (IN+) may charge the capacitor 414, charge the capacitor 426,flow through the inductor 422, and flow through the inductor 430 suchthat the output of the differential amplifier 402 is subject to arelatively high capacitance (e.g., the capacitance of the capacitor 414and the capacitance of the capacitor 426). Subjecting the output to thedifferential amplifier 402 to the relatively high capacitance may causethe power amplifier 400 to operate within the first frequency band.

In a similar manner, the transmission enable signal (TX_EN) may activatethe transistor 420 (e.g., a shunt-to-ground transistor), the firstenable signal (First_EN) may activate the transistor 432 (e.g., ashunt-to-ground transistor), and the third enable signal (Third_EN) maydeactivate the transistor 450. Thus the capacitor 416 may be shunt toground, additional current may charge the capacitor 428 and additionalcurrent may propagate through the inductor 430 (e.g., the inductor 430may be coupled to ground via the transistor 432), and the capacitor 446may be decoupled from ground to operate as a “floating” capacitor.Current based on the second differential input signal (IN−) may chargethe capacitor 416, charge the capacitor 428, flow through the inductor422, and flow through the inductor 430 such that the output of thedifferential amplifier 402 is subject to a relatively high capacitance(e.g., the capacitance of the capacitor 416 and the capacitance of thecapacitor 428). Subjecting the output of the differential amplifier 402to the relatively high capacitance may cause the power amplifier 400 tooperate within the first frequency band.

To operate in a second frequency band (e.g., a 5.6 GHz frequency band),the transmission enable signal (TX_EN) may activate the transistor 418and the capacitor 414 may be shunt to ground. In addition, the firstenable signal (First_EN) may disable the transistor 434 to decouple theinductor 430 from ground such that the capacitor 426 is a “floating”capacitor, and the third enable signal (Third_EN) may disable thetransistor 452 to decouple the inductor 448 from ground such that thecapacitor 444 is a “floating” capacitor. Current based on the firstdifferential input signal (IN+) may charge the capacitor 414 and flowthrough the inductor 422 such that the output of the differentialamplifier 402 is subject to reduced capacitance (e.g., a capacitancebased on the capacitor 414 as opposed to a capacitance based on thecapacitor 414 and the capacitor 426). Subjecting the output of thedifferential amplifier 402 to the reduced capacitance may cause thepower amplifier 400 to operate within the second frequency band.

In a similar manner, the transmission enable signal (TX_EN) may activatethe transistor 420 and the capacitor 416 may be shunt to ground. Inaddition, the first enable signal (First_EN) may disable the transistor432 to decouple the inductor 430 from ground such that the capacitor 428is a “floating” capacitor, and the third enable signal (Third_EN) maydisable the transistor 450 to decouple the inductor 448 from ground suchthat the capacitor 446 is a “floating” capacitor. Current based on thesecond differential input signal (IN−) may charge the capacitor 416 andflow through the inductor 422 such that the output of the differentialamplifier 402 is subject to a reduced capacitance (e.g., a capacitancebased on the capacitor 416 as opposed to a capacitance based on thecapacitor 416 and the capacitor 428). Subjecting the output of thedifferential amplifier 402 to the reduced capacitance may cause thepower amplifier 400 to operate within the second frequency band.

In an exemplary embodiment, the power amplifier 400 may concurrentlyoperate in the first frequency band and the second frequency band. Forexample, the second enable signal (Second_EN) may enable the transistors440, 442 such that the output of the differential amplifier 302 isadditionally subject to the capacitance of the capacitors 436, 438. Theincreased capacitance may cause the cause the power amplifier to operatewithin the first frequency band (e.g., the 2.4 GHz frequency band) inaddition to operating within the second frequency band. For example, theincreased capacitance may cause the inductive and capacitive elementscoupled to the output of the differential amplifier 302 to resonate atapproximately 2.4 GHz and at approximately 5.6 GHz.

To operate in a third frequency band (e.g., an 800 megahertz (MHz)frequency band), the transmission enable signal (TX_EN) may activate thetransistor 418, the first enable signal (First_EN) may deactivate thetransistor 434, and the third enable signal (Third_EN) may activate thetransistor 452. The capacitor 414 may be shunt to ground, the capacitor426 may operate as a “floating” capacitor, and additional current maycharge the capacitor 444 and additional current may propagate throughthe inductor 448 (e.g., the inductor 448 may be coupled to ground viathe transistor 452). In an exemplary embodiment, the capacitance of thecapacitor 444 may be greater than the capacitance of the capacitor 426such that the differential amplifier 402 is subject to a greatercapacitance when the capacitor 444 is “active” than when the capacitor426 is “active” (e.g., the first frequency band). As a non-limitingexample, the capacitor 444 may be a 5 pico-Farad (pF) capacitor and thecapacitor 426 may be a 2.5 pF capacitor. Subjecting the output of thedifferential amplifier 402 to the increased capacitance may cause thepower amplifier 400 to operate within the third frequency band.

In a similar manner, the transmission enable signal (TX_EN) may activatethe transistor 420, the first enable signal (First_EN) may deactivatethe transistor 432, and the third enable signal (Third_EN) may activatethe transistor 450. The capacitor 416 may be shunt to ground, thecapacitor 428 may operate as a “floating” capacitor, and additionalcurrent may charge the capacitor 446 and additional current maypropagate through the inductor 448 (e.g., the inductor 448 may becoupled to ground via the transistor 450). In an exemplary embodiment,the capacitance of the capacitor 446 may be greater than the capacitanceof the capacitor 428 such that the differential amplifier 402 is subjectto a greater capacitance when the capacitor 446 is “active” than whenthe capacitor 428 is “active” (e.g., the first frequency band).Subjecting the output of the differential amplifier 402 to the increasedcapacitance may cause the power amplifier 400 to operate within thethird frequency band.

The power amplifier 400 of FIG. 4 may reduce die area and increase costsavings by utilizing a single differential amplifier 402 (as opposed tomultiple transistor cores) to operate within one or more frequencybands. Two CLC networks may be coupled to the primary coil (e.g., theinductor 422) of the output balun. For example, a first CLC network(e.g., the capacitor 426, the inductor 430, and the capacitor 428) maybe coupled to the inductor 422, and a second CLC network (e.g., thecapacitor 444, the inductor 448, and the capacitor 446) may be coupledto the inductor 422. It will also be appreciated that operating thepower amplifier 400 at the third frequency band (e.g., 800 MHz) mayfacilitate communication based on an IEEE 802.11ah protocol.

Referring to FIG. 5, an exemplary embodiment of a multi-band driveramplifier 500 having a differential amplifier 502 including a singletransistor core is shown. In an exemplary embodiment, the driveramplifier 500 may correspond to, or may be included in, one or more ofthe driver amplifiers 290 pa, 290 pk, 290 sa, 290 sl of FIG. 2. Thedriver amplifier 500 may receive control signals from control circuitry(e.g., the control circuitry 284) to selectively operate in a firstfrequency band, a second frequency band, or any combination thereof.

The driver amplifier 500 includes an inductor-capacitor (LC) tank 501and a differential amplifier 502 (e.g., a transistor core). Thedifferential amplifier 502 may include a transistor 504, a transistor506, a transistor 508, and a transistor 510. In an exemplary embodiment,the transistors 504-510 of the differential amplifier 502 may be NMOStransistors. A source of the transistor 504 and a source of thetransistor 506 may be coupled to ground. A gate of the transistor 504and a gate of the transistor 506 may be coupled to receive adifferential input signal (IN+, IN). To illustrate, the gate of thetransistor 504 and the gate of the transistor 506 may be coupled toreceive a transmission signal from the data processor/controller 280 ofFIG. 2. A drain of the transistor 504 may be coupled to a source of thetransistor 508, and a drain of the transistor 506 may be coupled to asource of the transistor 510.

A drain of the transistor 508 may be coupled to a first terminal of atunable capacitor bank 512, and a drain of the transistor 510 may becoupled to a second terminal of the tunable capacitor bank 512. Thetunable capacitor bank 512 may be coupled in parallel with an inductor514. For example, the first terminal of the tunable capacitor bank 512may be coupled to a first terminal of the inductor 514, and the secondterminal of the tunable capacitor bank 512 may be coupled to a secondterminal of the inductor 514.

Components of the LC tank 501 (e.g., CLC network components) may beselectively coupled to the output of the differential amplifier 502 suchthat the driver amplifier 500 may operate in a single frequency band orsimultaneously operate in multiple frequency bands. For example, the CLCnetwork components include a capacitor 520, a capacitor 522, and aninductor 524. In an exemplary embodiment, the capacitor 520 and thecapacitor 522 may be tunable capacitors (e.g., tunable capacitor banks).A first terminal of the capacitor 520 may be coupled to the firstterminal of the inductor 514, and a second terminal of the capacitor 520may be coupled to a first terminal of the inductor 524. A first terminalof the capacitor 522 may be coupled to the second terminal of theinductor 514, and a second terminal of the capacitor 522 may be coupledto a second terminal of the inductor 524. A switch 516 may be coupled inparallel with (e.g., across from) the capacitor 520, a switch 518 may becoupled in parallel with (e.g., across from) the capacitor 522, and aswitch 526 may be coupled in parallel with (e.g., across from) theinductor 524.

During operation, the driver amplifier 500 may operate within a firstfrequency band (e.g., a 2 GHz frequency band), operate a secondfrequency band (e.g., a 5 GHz frequency band), or simultaneously operatein the first frequency band and the second frequency band. To operate inthe first frequency band, control signals (from the control circuitry284) may be provided to close the switch 526, open the switch 516, andopen the switch 518. Thus, when operating in the first frequency band,current may charge the capacitors 520, 522 and current may be shortedacross the switch 526 as opposed to propagating through the inductor524.

To operate in the second frequency band, control signals may be providedto close the switch 516, close the switch 518, and open the switch 526.Thus, when operating in the second frequency band, current may beshorted across the switches 516, 518 as opposed to charging thecapacitors 520, 522, respectively, and current may propagate through theinductor 524. To simultaneously operate in the first and secondfrequency bands, control signals may be provided to open each switch516, 518, 526. Thus, when simultaneously operating in first and secondfrequency bands, current may charge the capacitors 520, 522 andpropagate through the inductor 524.

The driver amplifier 500 of FIG. 5 may reduce die area and increase costsavings by utilizing a single differential amplifier 502 (as opposed tomultiple transistor cores) to operate within one or more frequencybands. It will also be appreciated that operating the driver amplifier500 within the first frequency band, the second frequency band, or acombination thereof, may facilitate communication based on wirelesscommunications standards, as described with respect to FIG. 3.

Referring to FIG. 6, another exemplary embodiment of a multi-band driveramplifier 600 having a differential amplifier 602 including a singletransistor core is shown. In an exemplary embodiment, the driveramplifier 600 may correspond to, or be included in, one or more of thedriver amplifiers 290 pa, 290 pk, 290 sa, 290 sl of FIG. 2. The driveramplifier 600 may receive control signals from control circuitry (e.g.,the control circuitry 284) to selectively operate in a first frequencyband, a second frequency band, or any combination thereof.

The driver amplifier 600 includes an inductor-capacitor (LC) tank 601and a differential amplifier 602 (e.g., a transistor core). Thedifferential amplifier 602 may include a transistor 604, a transistor606, a transistor 608, and a transistor 610. In an exemplary embodiment,the transistors 604-610 of the differential amplifier 602 may be NMOStransistors. A source of the transistor 604 and a source of thetransistor 606 may be coupled to ground. A gate of the transistor 604and a gate of the transistor 606 may be coupled to receive adifferential input signal (IN+, IN). To illustrate, the gate of thetransistor 604 and the gate of the transistor 606 may be coupled toreceive a transmission signal from the data processor/controller 280 ofFIG. 2. A drain of the transistor 604 may be coupled to a source of thetransistor 608, and a drain of the transistor 606 may be coupled to asource of the transistor 610.

A drain of the transistor 608 may be coupled to a first terminal of atunable capacitor bank 612, and a drain of the transistor 610 may becoupled to a second terminal of the tunable capacitor bank 612. Thetunable capacitor bank 612 may be coupled in parallel with an inductor614. For example, the first terminal of the tunable capacitor bank 612may be coupled to a first terminal of the inductor 614, and the secondterminal of the tunable capacitor bank 612 may be coupled to a secondterminal of the inductor 614.

Components of the LC tank 601 (e.g., CLC network components) may beselectively coupled to the output of the differential amplifier 602 suchthat the driver amplifier 600 may operate in multiple frequency bands.For example, the CLC network components include a capacitor 620, acapacitor 622, and an inductor 624. In an exemplary embodiment, thecapacitor 620 and the capacitor 622 may be tunable capacitors (e.g.,tunable capacitor banks). A first terminal of the capacitor 620 may becoupled to the first terminal of the inductor 614, and a second terminalof the capacitor 620 may be selectively coupled to a first terminal ofthe inductor 624 via a switch 630. A first terminal of the capacitor 622may be coupled to the second terminal of the inductor 614, and a secondterminal of the capacitor 622 may be selectively coupled to a secondterminal of the inductor 624 via a switch 632. A switch 616 may becoupled in parallel with (e.g., across from) the capacitor 620, and aswitch 618 may be coupled in parallel with (e.g., across from) thecapacitor 622. The first terminal of the inductor 614 may be selectivelycoupled to the second terminal of the inductor 624 via a switch 626, andthe second terminal of the inductor 614 may be selectively coupled tothe first terminal of the inductor 624 via a switch 628.

The driver amplifier 600 may operate in a substantially similar manneras the driver amplifier 500 of FIG. 5. For example, during operation,the driver amplifier 600 may operate within a first frequency band(e.g., a 2 GHz frequency band), operate a second frequency band (e.g., a5 GHz frequency band), or simultaneously operate in the first frequencyband and the second frequency band.

The effective inductance of the driver amplifier 600 may be tuned (e.g.,reduced or increased) using the switches 616, 618, 626, 628 to shiftfrequency ranges during operation. For example, control signals may openthe switch 616, open the switch 618, close the switch 626, and close theswitch 628 to reduce the effective inductance of the power amplifier600. Alternatively, control signals may close the switch 616, close theswitch 618, open the switch 626, and open the switch 628 to increase theeffective inductance of the power amplifier 600.

The driver amplifier 600 of FIG. 6 may reduce die area and increase costsavings by utilizing a single differential amplifier 602 (as opposed tomultiple transistor cores) to operate within one or more frequencybands. It will also be appreciated that the selectively activating theswitches 616, 618, 626, 628 may extend the inductive tuning range of thedriver amplifier 600 as compared to the inductor tuning range of thedriver amplifier 500 of FIG. 5.

Referring to FIG. 7, a flowchart that illustrates an exemplaryembodiment of a method 800 of operating a multi-band power amplifier isshown. In an illustrative embodiment, the method 700 may be performedusing the wireless device 110 of FIGS. 1-2, the power amplifier 300 ofFIG. 3, the power amplifier 400 of FIG. 4, or any combination thereof.

The method 700 includes amplifying a differential input signal at adifferential amplifier of a power amplifier, at 702. For example,referring to FIG. 3, the differential amplifier 302 of the poweramplifier 300 may amplify the differential input signal (IN+), (IN−).

A first output of the differential amplifier may provide an amplifiedsignal to a capacitor coupled to the first output of the differentialamplifier, at 704. The capacitor may be coupled to an inductor, and theinductor may be coupled to a second capacitor. For example, referring toFIG. 3, the amplified differential signal may be provided by the firstoutput of the differential amplifier 302 to the capacitor 326. Thecapacitor 326 is coupled to the inductor 330, and the inductor 330 iscoupled to the capacitor 336.

In an exemplary embodiment, the method 700 may include enabling a firsttransistor coupled to the inductor to operate the power amplifier in afirst frequency band. For example, referring to FIG. 3, the transistor334 may be enabled (e.g., activated) to operate the power amplifier 300in the first frequency band (e.g., the 2.4 GHz frequency band). Toillustrate, the inductor 330 may be coupled to ground via the transistor334 when the first enable signal (First_EN) has a logical high voltagelevel. Coupling the inductor 330 to ground may enable the poweramplifier 300 to transmit signals over the first frequency band.

In an exemplary embodiment, the method 700 may include enabling a secondtransistor coupled to the second capacitor to concurrently operate thepower amplifier in a first frequency band and a second frequency band.For example, referring to FIG. 3, the transistor 340 may be enabled toconcurrently operate the power amplifier 300 in the first frequency bandand the second frequency band (e.g., the 5.6 GHz frequency band). Toillustrate, the capacitor 336 may be coupled to ground via thetransistor 340 when the second enable signal (Second_EN) has a logicalhigh voltage level. Coupling the capacitor 336 to ground via thetransistor 340 may enable the power amplifier 300 to concurrentlytransmit signals over the first frequency band and the second frequencyband.

The method 700 of FIG. 7 may reduce die area and increase cost savingsby utilizing a single differential amplifier 302 (as opposed to multipletransistor cores) to operate within one or more frequency bands. Onecapacitor-inductor-capacitor (CLC) network may be coupled to the primarycoil (e.g., the inductor 322) of the output balun. For example, the CLCnetwork (e.g., the capacitor 326, the inductor 330, and the capacitor328) may be coupled to the inductor 322 and configured to operate withinthe first frequency band and decoupled from the inductor 322 to operatewithin the second frequency band.

In conjunction with the described embodiments, an apparatus includesfirst means for storing charge. For example, the first means for storingcharge may include the capacitor 336 of FIG. 3, the capacitor 436 ofFIG. 4, one or more other devices, circuits, or any combination thereof.The apparatus may also include first means for generating an inductancecoupled to the first means for storing charge. For example, the firstmeans for generating the inductance may include the inductor 330 of FIG.3, the inductor 430 of FIG. 4, one or more other devices, circuits, orany combination thereof.

The apparatus may also include second means for storing charge coupledto the first means for generating the inductance and to a first outputof a differential amplifier. For example, the second means for storingcharge may include the capacitor 326 of FIG. 3, the capacitor 426 ofFIG. 4, one or more other devices, circuits, or any combination thereof.

The apparatus may also include third means for storing charge coupled tothe first means for generating the inductance. For example, the thirdmeans for storing charge may include the capacitor 338 of FIG. 3, thecapacitor 438 of FIG. 4, one or more other devices, circuits, or anycombination thereof. The apparatus may also include fourth means forstoring charge coupled to the first means for generating the inductanceand to a second output of the differential amplifier. For example, thefourth means for storing charge may include the capacitor 328 of FIG. 3,the capacitor 428 of FIG. 4, one or more other devices, circuits, or anycombination thereof.

The apparatus may also include fifth means for storing charge coupled tothe second means for storing charge. For example, the fifth means forstoring charge may include the capacitor 444 of FIG. 4, one or moreother devices, circuits, or any combination thereof. The apparatus mayalso include second means for generating an inductance coupled to thefifth means for storing charge. For example, the second means forgenerating the inductance may include the inductor 448 of FIG. 4, one ormore other devices, circuits, or any combination thereof.

The apparatus may also include sixth means for storing charge coupled tothe fourth means for storing charge and to the second means forgenerating the inductance. For example, the sixth means for storingcharge may include the capacitor 446 of FIG. 4, one or more otherdevices, circuits, or any combination thereof. The apparatus may alsoinclude means for amplifying a transmission signal. For example, themeans for amplifying the transmission signal may include the poweramplifier 300 of FIG. 3, the power amplifier 400 of FIG. 4, one or moreother devices, circuits, or any combination thereof.

The apparatus may also include means for generating the transmissionsignal configured to provide the transmission signal to the means foramplifying the transmission signal. For example, the means forgenerating the transmission signal may include the driver amplifier 500of FIG. 5, the driver amplifier 600 of FIG. 6, one or more otherdevices, circuits, or any combination thereof.

The means for generating the transmission signal may include first meansfor switching coupled in parallel to seventh means for storing charge.For example, the first means for switching may include the switch 516 ofFIG. 5, one or more other devices, circuits, or any combination thereof.The seventh means for storing charge may include the capacitor 520 ofFIG. 5, one or more other devices, circuits, or any combination thereof.The means for generating the transmission signal may also include secondmeans for switching coupled in parallel to eighth means for storingcharge. For example, the second means for switching may include theswitch 518 of FIG. 5, one or more other devices, circuits, or anycombination thereof. The eighth means for storing charge may include thecapacitor 522 of FIG. 5, one or more other devices, circuits, or anycombination thereof. The means for generating the transmission signalmay also include third means for switching coupled in parallel to thirdmeans for generating an inductance. For example, the third means forswitching may include the switch 526 of FIG. 5, one or more otherdevices, circuits, or any combination thereof. The third means forgenerating the inductance may include the inductor 524 of FIG. 5, theinductor 624 of FIG. 6, one or more other devices, circuits, or anycombination thereof.

The means for generating the transmission signal may also include fourthmeans for switching configured to selectively coupled a first terminalof a fourth means for generating an inductance to a second terminal ofthe third means for generating the inductance. For example, the fourthmeans for switching may include the switch 626 of FIG. 6, one or moreother devices, circuits, or any combination thereof. The fourth meansfor generating the inductance may include the inductor 624 of FIG. 6,one or more other devices, circuits, or any combination thereof.

The means for generating the transmission signal may also include fifthmeans for switching configured to selectively couple a second terminalof the fourth means for generating the inductance to a first terminal ofthe third means for generating the inductance. For example, the fifthmeans for switching may include the switch 628 of FIG. 6, one or moreother devices, circuits, or any combination thereof.

The previous description of the disclosed embodiments is provided toenable a person skilled in the art to make or use the disclosedembodiments. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the principles defined hereinmay be applied to other embodiments without departing from the scope ofthe disclosure. Thus, the present disclosure is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope possible consistent with the principles and novel features asdefined by the following claims.

What is claimed is:
 1. An apparatus comprising: a first capacitor; an inductor coupled to the first capacitor; and a second capacitor coupled to the inductor and to a first output of a differential amplifier.
 2. The apparatus of claim 1, wherein the first capacitor is coupled to a first transistor, and wherein the inductor is coupled to a second transistor.
 3. The apparatus of claim 1, further comprising: a third capacitor coupled to the inductor; and a fourth capacitor coupled to the inductor and to a second output of the differential amplifier.
 4. The apparatus of claim 3, wherein the third capacitor is coupled to a third transistor.
 5. The apparatus of claim 3, further comprising: a fifth capacitor coupled to the second capacitor; a second inductor coupled to the fifth capacitor; and a sixth capacitor coupled to the fourth capacitor and coupled to the second inductor.
 6. The apparatus of claim 1, further comprising a power amplifier that is tunable in broadband, wherein the power amplifier includes the first capacitor, the inductor, and the second capacitor.
 7. The apparatus of claim 1, further comprising a driver amplifier configured to provide a transmission signal to the power amplifier, the driver amplifier comprising: a first switch coupled in parallel to a seventh capacitor; a second switch coupled in parallel to an eighth capacitor; and a third switch coupled in parallel to a third inductor, wherein the first switch, the second switch, and the third switch are selectively activated to adjust an operating frequency of the driver amplifier.
 8. The apparatus of claim 7, wherein the seventh capacitor and the eighth capacitor are tunable.
 9. The apparatus of claim 7, wherein the driver amplifier further comprises: a fourth switch configured to selectively couple a first terminal of a fourth inductor to a second terminal of the third inductor; and a fifth switch configured to selectively couple a second terminal of the fourth inductor to a first terminal of the third inductor; wherein the fourth switch and the fifth switch are selectively activated to adjust an inductance of the driver amplifier.
 10. An apparatus comprising: first means for storing charge; first means for generating an inductance coupled to the first means for storing charge; and second means for storing charge coupled to the first means for generating the inductance and to a first output of a differential amplifier.
 11. The apparatus of claim 10, wherein the first means for storing charge is coupled to a first transistor, and wherein the first means for generating the inductance is coupled to a second transistor.
 12. The apparatus of claim 10, further comprising: third means for storing charge coupled to the first means for generating the inductance; and fourth means for storing charge coupled to the first means for generating the inductance and to a second output of the differential amplifier.
 13. The apparatus of claim 12, wherein the first means for storing charge and the third means for storing charge are tunable.
 14. The apparatus of claim 12, further comprising: fifth means for storing charge coupled to the second means for storing charge; second means for generating an inductance coupled to the fifth means for storing charge; and sixth means for storing charge coupled the fourth means for storing charge and to the second means for generating the inductance.
 15. The apparatus of claim 10, further comprising means for amplifying a transmission signal, wherein the means for amplifying the transmission signal includes the first means for storing charge, the first means for generating the inductance, and the second means for storing charge.
 16. The apparatus of claim 15, further comprising means for generating the transmission signal configured to provide the transmission signal to the means for amplifying the transmission signal, the means for generating the transmission signal comprising: first means for switching coupled in parallel to seventh means for storing charge; second means for switching coupled in parallel to eighth means for storing charge; and third means for switching coupled in parallel to third means for generating an inductance, wherein the first means for switching, the second means for switching, and the third means for switching are selectively activated to adjust an operating frequency of the means for generating the transmission signal.
 17. The apparatus of claim 16, wherein the means for generating the transmission signal further comprises: fourth means for switching configured to selectively coupled a first terminal of a fourth means for generating an inductance to a second terminal of the third means for generating the inductance; and fifth means for switching configured to selectively couple a second terminal of the fourth means for generating the inductance to a first terminal of the third means for generating the inductance; wherein the fourth means for switching and the fifth means for switching are selectively activated to adjust an inductance of the means for generating the transmission signal.
 18. A method comprising: amplifying a differential input signal at a differential amplifier of a power amplifier; and providing the amplified differential signal at a first output of the differential amplifier to a capacitor, wherein the capacitor is coupled to an inductor and the inductor is coupled to a second capacitor.
 19. The method of claim 18, further comprising enabling a first transistor coupled to the inductor to operate the power amplifier in a first frequency band.
 20. The method of claim 18, further comprising enabling a second transistor coupled to the second capacitor to concurrently operate the power amplifier in a first frequency band and a second frequency band. 